Spatial guardbands for terrestrial reuse of satellite frequencies

ABSTRACT

Satellite radiotelephone systems include a space-based component that is configured to provide wireless radiotelephone communications in a satellite footprint over a satellite radiotelephone frequency band. The satellite footprint is divided into a plurality of satellite cells, in which satellite radiotelephone frequencies of the satellite radiotelephone frequency band are spatially reused. An ancillary terrestrial network is configured to terrestrially reuse at least one of the ancillary radiotelephone frequencies that is used in a satellite cell in the satellite footprint, outside the cell and in some embodiments separated therefrom by a spatial guardband. The spatial guardband may be sufficiently large to reduce or prevent interference between the at least one of the satellite radiotelephone frequencies that is used in the satellite cell in the satellite footprint, and the at least one of the satellite radiotelephone frequencies that is terrestrially reused outside the satellite cell and separated therefrom by the spatial guardband. The spatial guardband may be about half a radius of a satellite cell in width.

CROSS-REFERENCE TO PROVISIONAL APPLICATION

[0001] This application claims the benefit of provisional ApplicationNo. 60/322,240, filed Sep. 14, 2001, entitled Systems and Methods forTerrestrial Re-Use of Mobile Satellite Spectrum, and provisionalApplication Serial No. 60/347,173, filed Jan. 9, 2002, entitled SpatialGuardbands for Terrestrial Reuse of Satellite Frequencies. Thisapplication also claims the benefit of application Ser. No. 10/074,097,filed Jan. 9, 2002, entitled Systems and Methods for Terrestrial Reuseof Cellular Satellite Frequency Spectrum. All of these applications areassigned to the assignee of the present application, the disclosures ofall of which are hereby incorporated herein by reference in theirentirety as if set forth fully herein.

FIELD OF THE INVENTION

[0002] This invention relates to radiotelephone communications systemsand methods, and more particularly to terrestrial cellular and satellitecellular radiotelephone communications systems and methods.

BACKGROUND OF THE INVENTION

[0003] Satellite radiotelephone communications systems and methods arewidely used for radiotelephone communications. Satellite radiotelephonecommunications systems and methods generally employ at least onespace-based component, such as one or more satellites that areconfigured to wirelessly communicate with a plurality of satelliteradiotelephones.

[0004] A satellite radiotelephone communications system or method mayutilize a single antenna beam covering an entire area served by thesystem. Alternatively, in cellular satellite radiotelephonecommunications systems and methods, multiple beams are provided, each ofwhich can serve distinct geographical areas in the overall serviceregion, to collectively serve an overall satellite footprint. Thus, acellular architecture similar to that used in conventional terrestrialcellular radiotelephone systems and methods can be implemented incellular satellite-based systems and methods. The satellite typicallycommunicates with radiotelephones over a bidirectional communicationspathway, with radiotelephone communication signals being communicatedfrom the satellite to the radiotelephone over a downlink or forwardlink, and from the radiotelephone to the satellite over an uplink orreturn link.

[0005] The overall design and operation of cellular satelliteradiotelephone systems and methods are well known to those having skillin the art, and need not be described further herein. Moreover, as usedherein, the term “radiotelephone” includes cellular and/or satelliteradiotelephones with or without a multi-line display; PersonalCommunications System (PCS) terminals that may combine a radiotelephonewith data processing, facsimile and/or data communications capabilities;Personal Digital Assistants (PDA) that can include a radio frequencytransceiver and a pager, Internet/intranet access, Web browser,organizer, calendar and/or a global positioning system (GPS) receiver;and/or conventional laptop and/or palmtop computers or other appliances,which include a radio frequency transceiver.

[0006] As is well known to those having skill in the art, terrestrialnetworks can enhance cellular satellite radiotelephone systemavailability, efficiency and/or economic viability by terrestriallyreusing at least some of the frequency bands that are allocated tocellular satellite radiotelephone systems. In particular, it is knownthat it may be difficult for cellular satellite radiotelephone systemsto reliably serve densely populated areas, because the satellite signalmay be blocked by high-rise structures and/or may not penetrate intobuildings. As a result, the satellite spectrum may be underutilized orunutilized in such areas. The use of terrestrial retransmission canreduce or eliminate this problem.

[0007] Moreover, the capacity of the overall system can be increasedsignificantly by the introduction of terrestrial retransmission, sinceterrestrial frequency reuse can be much denser than that of asatellite-only system. In fact, capacity can be enhanced where it may bemostly needed, i.e., densely populated urban/industrial/commercialareas. As a result, the overall system can become much more economicallyviable, as it may be able to serve a much larger subscriber base.Finally, satellite radiotelephones for a satellite radiotelephone systemhaving a terrestrial component within the same satellite frequency bandand using substantially the same air interface for both terrestrial andsatellite communications can be more cost effective and/or aestheticallyappealing. Conventional dual band/dual mode alternatives, such as thewell known Thuraya, Iridium and/or Globalstar dual modesatellite/terrestrial radiotelephone systems, may duplicate somecomponents, which may lead to increased cost, size and/or weight of theradiotelephone.

[0008] One example of terrestrial reuse of satellite frequencies isdescribed in U.S. Pat. No. 5,937,332 to the present inventor Karabinisentitled Satellite Telecommunications Repeaters and RetransmissionMethods, the disclosure of which is hereby incorporated herein byreference in its entirety as if set forth fully herein. As describedtherein, satellite telecommunications repeaters are provided whichreceive, amplify, and locally retransmit the downlink signal receivedfrom a satellite thereby increasing the effective downlink margin in thevicinity of the satellite telecommunications repeaters and allowing anincrease in the penetration of uplink and downlink signals intobuildings, foliage, transportation vehicles, and other objects which canreduce link margin. Both portable and non-portable repeaters areprovided. See the abstract of U.S. Pat. No. 5,937,332.

[0009] In view of the above discussion, there continues to be a need forsystems and methods for terrestrial reuse of cellular satellitefrequencies that can allow improved reliability, capacity, costeffectiveness and/or aesthetic appeal for cellular satelliteradiotelephone systems, methods and/or satellite radiotelephones.

SUMMARY OF THE INVENTION

[0010] Satellite radiotelephone systems according to some embodiments ofthe present invention include a space-based component that is configuredto provide wireless radiotelephone communications in a satellitefootprint over a satellite radiotelephone frequency band. The satellitefootprint is divided into a plurality of satellite cells, in whichsatellite radiotelephone frequencies of the satellite radiotelephonefrequency band are spatially reused. An ancillary terrestrial network isconfigured to terrestrially reuse at least one of the satelliteradiotelephone frequencies that is used in a predetermined satellitecell in the satellite footprint, outside the predetermined cell and, insome embodiments, separated therefrom by a spatial guardband. Thus, insome embodiments of the invention, the ancillary terrestrial network isconfigured to reuse at least one of the satellite radiotelephonefrequencies that is used in a predetermined satellite cell in thesatellite footprint, such that the signal strength of the terrestriallyreused frequency, as received by the space-based component over thepredetermined satellite cell, defines a spatial guardband bounding thesatellite cell.

[0011] In some embodiments, the spatial guardband is sufficiently largeto reduce interference between the at least one of the satelliteradiotelephone frequencies that is used in the predetermined satellitecell in the satellite footprint for satellite communications, and the atleast one of the satellite radiotelephone frequencies that isterrestrially reused outside the predetermined satellite cell andseparated therefrom by the spatial guardband. In still otherembodiments, the spatial guardband is sufficiently large to preventinterference between the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint, and the at least one of the satelliteradiotelephone frequencies that is terrestrially reused outside thepredetermined satellite cell and separated therefrom by the spatialguardband. In yet other embodiments of the present invention, thespatial guardband is about half a radius of a satellite cell in width.

[0012] In some embodiments of the present invention, the spatialguardband is used to define regions for transmission (downlink) by thespace-based component and the ancillary terrestrial network. In otherembodiments, the spatial guardband is used to define regions forreception (uplink) by the space-based component and the ancillaryterrestrial network. In still other embodiments, the spatial guardbandis used to define regions both for transmitting and for receiving. Inyet other embodiments, interference is reduced by transmitting and/orreceiving the at least one of the satellite radiotelephone frequenciesthat is used in the predetermined satellite cell in the satellitefootprint, and at least one other frequency that is used by thespace-based component in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband.

[0013] Other embodiments of the present invention also include aninterference reducer that is responsive to the space-based component andto the ancillary terrestrial network. The interference reducer isconfigured to reduce interference from wireless communications that arereceived by the space-based component from a first radiotelephone in thesatellite footprint over the satellite radiotelephone frequency band,using wireless communications that are received by the ancillaryterrestrial network from a second radiotelephone in the satellitefootprint over the satellite radiotelephone frequency band.

[0014] In still other embodiments of the present invention, theancillary terrestrial network is divided into a plurality of ancillaryterrestrial network cells in which frequencies of the satelliteradiotelephone frequency band are spatially reused. In theseembodiments, the ancillary terrestrial network is further configured toterrestrially reuse at least one of the satellite radiotelephonefrequencies that is used in a predetermined satellite cell in thesatellite footprint, in the ancillary terrestrial network cells that areoutside the predetermined cell and separated therefrom by the spatialguardband. In still other embodiments, the ancillary terrestrial networkis further configured to terrestrially reuse at least one of thesatellite radiotelephone frequencies that is used in the predeterminedsatellite cell in the satellite footprint, by not (i.e., refrainingfrom) terrestrially reusing the at least one of the satelliteradiotelephone frequencies that is used in the predetermined satellitecell in the satellite footprint, within the predetermined cell or withinthe spatial guardband.

[0015] In still other embodiments of the present invention, theancillary terrestrial network comprises a plurality of ancillaryterrestrial components (e.g., base stations or groups of base stations).At least a first one of the ancillary terrestrial components is locatedin or close to the predetermined satellite cell, and is configured notto terrestrially reuse the at least one of the satellite radiotelephonefrequencies that is used in the predetermined cell. At least a secondancillary terrestrial component is located outside the predeterminedsatellite cell and separated therefrom by the spatial guardband, and isconfigured to terrestrially reuse the at least one of the satelliteradiotelephone frequencies that is used in the predetermined satellitecell.

[0016] In other embodiments of the present invention, the ancillaryterrestrial network is configured to itself determine portions thereofthat are located outside the predetermined satellite cell and separatedtherefrom by the spatial guardband. In some embodiments, thisdetermination may take place by using information derived from receivingand/or processing at least one of the satellite radiotelephonefrequencies of the satellite radiotelephone frequency band. In stillother embodiments, the satellite radiotelephone frequencies include aplurality of Broadcast Control CHannel (BCCH) frequencies, and theancillary terrestrial network receives and/or processes signal strengthand/or content of at least one of the BCCH frequencies, in order todetermine portions thereof that are located outside the predeterminedcell and separated therefrom by the spatial guardband.

[0017] Moreover, in other embodiments, the ancillary terrestrial networkcomprises a plurality of ancillary terrestrial components, each of whichis configured to determine whether it is located outside thepredetermined satellite cell, and separated therefrom by the spatialguardband. In still other embodiments, the ancillary terrestrial networkcomprises a plurality of ancillary terrestrial components, at least oneof which is configured to determine whether it is located outside thepredetermined satellite cell and separated therefrom by the spatialguardband, and to transmit results of the determination to at least asecond one of the plurality of ancillary terrestrial components.

[0018] Finally, it will be understood that the present invention may beembodied as systems, ancillary terrestrial components and/or methods.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a schematic diagram of cellular radiotelephone systemsand methods according to embodiments of the invention.

[0020]FIG. 2 is a block diagram of adaptive interference reducersaccording to embodiments of the present invention.

[0021]FIG. 3 is a spectrum diagram that illustrates satellite L-bandfrequency allocations.

[0022]FIG. 4 is a schematic diagram of cellular satellite systems andmethods according to other embodiments of the present invention.

[0023]FIG. 5 illustrates time division duplex frame structures accordingto embodiments of the present invention.

[0024]FIG. 6 is a block diagram of architectures of ancillaryterrestrial components according to embodiments of the invention.

[0025]FIG. 7 is a block diagram of architectures of reconfigurableradiotelephones according to embodiments of the invention.

[0026]FIG. 8 graphically illustrates mapping of monotonically decreasingpower levels to frequencies according to embodiments of the presentinvention.

[0027]FIG. 9 illustrates an ideal cell that is mapped to three powerregions and three associated carrier frequencies according toembodiments of the invention.

[0028]FIG. 10 depicts a realistic cell that is mapped to three powerregions and three associated carrier frequencies according toembodiments of the invention.

[0029]FIG. 11 illustrates two or more contiguous slots in a frame thatare unoccupied according to embodiments of the present invention.

[0030]FIG. 12 illustrates loading of two or more contiguous slots withlower power transmissions according to embodiments of the presentinvention.

[0031]FIGS. 13 and 14 schematically illustrate spatial guardbands forterrestrial reuse of satellite frequencies in 7 and 9 cell frequencyreuse patterns, respectively.

DETAILED DESCRIPTION

[0032] The present invention now will be described more fullyhereinafter with reference to the accompanying drawings, in whichtypical embodiments of the invention are shown. This invention may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. Like numbers refer to like elements throughout.

[0033]FIG. 1 is a schematic diagram of cellular satellite radiotelephonesystems and methods according to embodiments of the invention. As shownin FIG. 1, these cellular satellite radiotelephone systems and methods100 include at least one Space-Based Component (SBC) 110, such as asatellite. The space-based component 110 is configured to transmitwireless communications to a plurality of radiotelephones 120 a, 120 bin a satellite footprint comprising one or more satellite radiotelephonecells 130-130″″ over one or more satellite radiotelephone forward link(downlink) frequencies f_(D). The space-based component 110 isconfigured to receive wireless communications from, for example, a firstradiotelephone 120 a in the satellite radiotelephone cell 130 over asatellite radiotelephone return link (uplink) frequency f_(U). Anancillary terrestrial network, comprising at least one ancillaryterrestrial component 140, which may include an antenna 140 a and anelectronics system 140 b, is configured to receive wirelesscommunications from, for example, a second radiotelephone 120 b in theradiotelephone cell 130 over the satellite radiotelephone uplinkfrequency, denoted f′_(U), which may be the same as f_(U). Thus, asillustrated in FIG. 1, radiotelephone 120 a may be communicating withthe space-based component 110 while radiotelephone 120 b may becommunicating with the ancillary terrestrial component 140. As shown inFIG. 1, the space-based component 110 also undesirably receives thewireless communications from the second radiotelephone 120 b in thesatellite radiotelephone cell 130 over the satellite radiotelephonefrequency f′_(U) as interference. More specifically, a potentialinterference path is shown at 150. In this potential interference path150, the return link signal of the second radiotelephone 120 b atcarrier frequency f′_(U) interferes with satellite communications. Thisinterference would generally be strongest when f′_(U)=f_(U), because, inthat case, the same return link frequency would be used for space-basedcomponent and ancillary terrestrial component communications over thesame satellite radiotelephone cell, and no spatial discriminationbetween satellite radiotelephone cells would appear to exist.

[0034] Still referring to FIG. 1, embodiments of satelliteradiotelephone systems/methods 100 can include at least one gateway 160that can include an antenna 160 a and an electronics system 160 b thatcan be connected to other networks 162 including terrestrial and/orother radiotelephone networks. The gateway 160 also communicates withthe space-based component 110 over a satellite feeder link 112. Thegateway 160 also communicates with the ancillary terrestrial component140, generally over a terrestrial link 142.

[0035] Still referring to FIG. 1, an Interference Reducer (IR) 170 aalso may be provided at least partially in the ancillary terrestrialcomponent electronics system 140 b. Alternatively or additionally, aninterference reducer 170 b may be provided at least partially in thegateway electronics system 160 b. In yet other alternatives, theinterference reducer may be provided at least partially in othercomponents of the cellular satellite system/method 100 instead of or inaddition to the interference reducer 170 a and/or 170 b. Theinterference reducer is responsive to the space-based component 110 andto the ancillary terrestrial component 140, and is configured to reducethe interference from the wireless communications that are received bythe space-based component 110 and is at least partially generated by thesecond radiotelephone 120 b in the satellite radiotelephone cell 130over the satellite radiotelephone frequency f′_(U). The interferencereducer 170 a and/or 170 b uses the wireless communications f′_(U) thatare intended for the ancillary terrestrial component 140 from the secondradiotelephone 120 b in the satellite radiotelephone cell 130 using thesatellite radiotelephone frequency f′_(U) to communicate with theancillary terrestrial component 140.

[0036] In embodiments of the invention, as shown in FIG. 1, theancillary terrestrial component 140 generally is closer to the first andsecond radiotelephones 120 a and 120 b, respectively, than is thespace-based component 110, such that the wireless communications fromthe second radiotelephone 120 b are received by the ancillaryterrestrial component 140 prior to being received by the space-basedcomponent 110. The interference reducer 170 a and/or 170 b is configuredto generate an interference cancellation signal comprising, for example,at least one delayed replica of the wireless communications from thesecond radiotelephone 120 b that are received by the ancillaryterrestrial component 140, and to subtract the delayed replica of thewireless communications from the second radiotelephone 120 b that arereceived by the ancillary terrestrial component 140 from the wirelesscommunications that are received from the space-based component 110. Theinterference reduction signal may be transmitted from the ancillaryterrestrial component 140 to the gateway 160 over link 142 and/or usingother conventional techniques.

[0037] Thus, adaptive interference reduction techniques may be used toat least partially cancel the interfering signal, so that the same, orother nearby, satellite radiotelephone uplink frequency can be used in agiven cell for communications by radiotelephones 120 with the satellite110 and with the ancillary terrestrial component 140. Accordingly, allfrequencies that are assigned to a given cell 130 may be used for bothradiotelephone 120 communications with the space-based component 110 andwith the ancillary terrestrial component 140. Conventional systems mayavoid terrestrial reuse of frequencies within a given satellite cellthat are being used within the satellite cell for satellitecommunications. Stated differently, conventionally, only frequenciesused by other satellite cells may be candidates for terrestrial reusewithin a given satellite cell. Beam-to-beam spatial isolation that isprovided by the satellite system was relied upon to reduce or minimizethe level of interference from the terrestrial operations into thesatellite operations. In sharp contrast, embodiments of the inventioncan use an interference reducer to allow all frequencies assigned to asatellite cell to be used terrestrially and for satellite radiotelephonecommunications.

[0038] Embodiments of the invention according to FIG. 1 may arise from arealization that the return link signal from the second radiotelephone120 b at f′_(U) generally will be received and processed by theancillary terrestrial component 140 much earlier relative to the timewhen it will arrive at the satellite gateway 160 from the space-basedcomponent 110 via the interference path 150. Accordingly, theinterference signal at the satellite gateway 160 b can be at leastpartially canceled. Thus, as shown in FIG. 1, an interferencecancellation signal, such as the demodulated ancillary terrestrialcomponent signal, can be sent to the satellite gateway 160 b by theinterference reducer 170 a in the ancillary terrestrial component 140,for example using link 142. In the interference reducer 170 b at thegateway 160 b, a weighted (in amplitude and/or phase) replica of thesignal may be formed using, for example, adaptive transversal filtertechniques that are well known to those having skill in the art. Then, atransversal filter output signal is subtracted from the aggregatereceived satellite signal at frequency f′_(U) that contains desired aswell as interference signals. Thus, the interference cancellation neednot degrade the signal-to-noise ratio of the desired signal at thegateway 160, because a regenerated (noise-free) terrestrial signal, forexample as regenerated by the ancillary terrestrial component 140, canbe used to perform interference suppression.

[0039]FIG. 2 is a block diagram of embodiments of adaptive interferencecancellers that may be located in the ancillary terrestrial component140, in the gateway 160, and/or in another component of the cellularradiotelephone system 100. As shown in FIG. 2, one or more controlalgorithms 204, known to those having skill in the art, may be used toadaptively adjust the coefficients of a plurality of transversal filters202 a-202 n. Adaptive algorithms, such as Least Mean Square Error(LMSE), Kalman, Fast Kalman, Zero Forcing and/or various combinationsthereof or other techniques may be used. It will be understood by thosehaving skill in the art that the architecture of FIG. 2 may be used withan LMSE algorithm. However, it also will be understood by those havingskill in the art that conventional architectural modifications may bemade to facilitate other control algorithms.

[0040] Additional embodiments of the invention now will be describedwith reference to FIG. 3, which illustrates L-band frequency allocationsincluding cellular radiotelephone system forward links and return links.As shown in FIG. 3, the space-to-ground L-band forward link (downlink)frequencies are assigned from 1525 MHz to 1559 MHz. The ground-to-spaceL-band return link (uplink) frequencies occupy the band from 1626.5 MHzto 1660.5 MHz. Between the forward and return L-band links lie theGPS/GLONASS radionavigation band (from 1559 MHz to 1605 MHz).

[0041] In the detailed description to follow, GPS/GLONASS will bereferred to simply as GPS for the sake of brevity. Moreover, theacronyms ATC and SBC will be used for the ancillary terrestrialcomponent and the space-based component, respectively, for the sake ofbrevity.

[0042] As is known to those skilled in the art, GPS receivers may beextremely sensitive since they are designed to operate on very weakspread-spectrum radionavigation signals that arrive on the earth from aGPS satellite constellation. As a result, GPS receivers may to be highlysusceptible to in-band interference. ATCs that are configured to radiateL-band frequencies in the forward satellite band (1525 to 1559 MHz) canbe designed with very sharp out-of-band emissions filters to satisfy thestringent out-of-band spurious emissions desires of GPS.

[0043] Referring again to FIG. 1, some embodiments of the invention canprovide systems and methods that can allow an ATC 140 to configureitself in one of at least two modes. In accordance with a first mode,which may be a standard mode and may provide highest capacity, the ATC140 transmits to the radiotelephones 120 over the frequency range from1525 MHz to 1559 MHz, and receives transmissions from theradiotelephones 120 in the frequency range from 1626.5 MHz to 1660.5MHz, as illustrated in FIG. 3. In contrast, in a second mode ofoperation, the ATC 140 transmits wireless communications to theradiotelephones 120 over a modified range of satellite band forward link(downlink) frequencies. The modified range of satellite band forwardlink frequencies may be selected to reduce, compared to the unmodifiedrange of satellite band forward link frequencies, interference withwireless receivers such as GPS receivers that operate outside the rangeof satellite band forward link frequencies.

[0044] Many modified ranges of satellite band forward link frequenciesmay be provided according to embodiments of the present invention. Insome embodiments, the modified range of satellite band forward linkfrequencies can be limited to a subset of the original range ofsatellite band forward link frequencies, so as to provide a guard bandof unused satellite band forward link frequencies. In other embodiments,all of the satellite band forward link frequencies are used, but thewireless communications to the radiotelephones are modified in a mannerto reduce interference with wireless receivers that operate outside therange of satellite band forward link frequencies. Combinations andsubcombinations of these and/or other techniques also may be used, aswill be described below.

[0045] It also will be understood that embodiments of the invention thatwill now be described in connection with FIGS. 4-12 will be described interms of multiple mode ATCs 140 that can operate in a first standardmode using the standard forward and return links of FIG. 3, and in asecond or alternate mode that uses a modified range of satellite bandforward link frequencies and/or a modified range of satellite bandreturn link frequencies. These multiple mode ATCs can operate in thesecond, non-standard mode, as long as desirable, and can be switched tostandard mode otherwise. However, other embodiments of the presentinvention need not provide multiple mode ATCs but, rather, can provideATCs that operate using the modified range of satellite band forwardlink and/or return link frequencies.

[0046] Embodiments of the invention now will be described, wherein anATC operates with an SBC that is configured to receive wirelesscommunications from radiotelephones over a first range of satellite bandreturn link frequencies and to transmit wireless communications to theradiotelephones over a second range of satellite band forward linkfrequencies that is spaced apart from the first range. According tothese embodiments, the ATC is configured to use at least one timedivision duplex frequency to transmit wireless communications to theradiotelephones and to receive wireless communications from theradiotelephones at different times. In particular, in some embodiments,the at least one time division duplex frequency that is used to transmitwireless communications to the radiotelephones and to receive wirelesscommunications from the radiotelephones at different times, comprises aframe including a plurality of slots. At least a first one of the slotsis used to transmit wireless communications to the radiotelephones andat least a second one of the slots is used to receive wirelesscommunications from the radiotelephones. Thus, in some embodiments, theATC transmits and receives, in Time Division Duplex (TDD) mode, usingfrequencies from 1626.5 Mhz to 1660.5 Mhz. In some embodiments, all ATCsacross the entire network may have the statedconfiguration/reconfiguration flexibility. In other embodiments, onlysome ATCs may be reconfigurable.

[0047]FIG. 4 illustrates satellite systems and methods 400 according tosome embodiments of the invention, including an ATC 140 communicatingwith a radiotelephone 120 b using a carrier frequency f′_(U) in TDDmode. FIG. 5 illustrates an embodiment of a TDD frame structure.Assuming full-rate GSM (eight time slots per frame), up to fourfull-duplex voice circuits can be supported by one TDD carrier. As shownin FIG. 5, the ATC 140 transmits to the radiotelephone 120 b over, forexample, time slot number 0. The radiotelephone 120 b receives andreplies back to the ATC 140 over, for example, time slot number 4. Timeslots number 1 and 5 may be used to establish communications withanother radiotelephone, and so on.

[0048] A Broadcast Control CHannel (BCCH) is preferably transmitted fromthe ATC 140 in standard mode, using a carrier frequency from below anyguard band exclusion region. In other embodiments, a BCCH also can bedefined using a TDD carrier. In any of these embodiments,radiotelephones in idle mode can, per established GSM methodology,monitor the BCCH and receive system-level and paging information. When aradiotelephone is paged, the system decides what type of resource toallocate to the radiotelephone in order to establish the communicationslink. Whatever type of resource is allocated for the radiotelephonecommunications channel (TDD mode or standard mode), the information iscommunicated to the radiotelephone, for example as part of the callinitialization routine, and the radiotelephone configures itselfappropriately.

[0049] It may be difficult for the TDD mode to co-exist with thestandard mode over the same ATC, due, for example, to the ATC receiverLNA stage. In particular, assuming a mixture of standard and TDD modeGSM carriers over the same ATC, during the part of the frame when theTDD carriers are used to serve the forward link (when the ATC istransmitting TDD) enough energy may leak into the receiver front end ofthe same ATC to desensitize its LNA stage.

[0050] Techniques can be used to suppress the transmitted ATC energyover the 1600 Mhz portion of the band from desensitizing the ATC'sreceiver LNA, and thereby allow mixed standard mode and TDD frames. Forexample, isolation between outbound and inbound ATC front ends and/orantenna system return loss may be increased or maximized. A switchableband-reject filter may be placed in front of the LNA stage. This filterwould be switched in the receiver chain (prior to the LNA) during thepart of the frame when the ATC is transmitting TDD, and switched outduring the rest of the time. An adaptive interference canceller can beconfigured at RF (prior to the LNA stage). If such techniques are used,suppression of the order of 70 dB can be attained, which may allow mixedstandard mode and TDD frames. However, the ATC complexity and/or costmay increase.

[0051] Thus, even though ATC LNA desensitization may be reduced oreliminated, it may use significant special engineering and attention andmay not be economically worth the effort. Other embodiments, therefore,may keep TDD ATCs pure TDD, with the exception, perhaps, of the BCCHcarrier which may not be used for traffic but only for broadcasting overthe first part of the frame, consistent with TDD protocol. Moreover,Random Access CHannel (RACH) bursts may be timed so that they arrive atthe ATC during the second half of the TDD frame. In some embodiments,all TDD ATCs may be equipped to enable reconfiguration in response to acommand.

[0052] It is well recognized that during data communications or otherapplications, the forward link may use transmissions at higher ratesthan the return link. For example, in web browsing with aradiotelephone, mouse clicks and/or other user selections typically aretransmitted from the radiotelephone to the system. The system, however,in response to a user selection, may have to send large data files tothe radiotelephone. Hence, other embodiments of the invention may beconfigured to enable use of an increased or maximum number of time slotsper forward GSM carrier frame, to provide a higher downlink data rate tothe radiotelephones.

[0053] Thus, when a carrier frequency is configured to provide servicein TDD mode, a decision may be made as to how many slots will beallocated to serving the forward link, and how many will be dedicated tothe return link. Whatever the decision is, it may be desirable that itbe adhered to by all TDD carriers used by the ATC, in order to reduce oravoid the LNA desensitization problem described earlier. In voicecommunications, the partition between forward and return link slots maybe made in the middle of the frame as voice activity typically isstatistically bidirectionally symmetrical. Hence, driven by voice, thecenter of the frame may be where the TDD partition is drawn.

[0054] To increase or maximize forward link throughput in data mode,data mode TDD carriers according to embodiments of the invention may usea more spectrally efficient modulation and/or protocol, such as the EDGEmodulation and/or protocol, on the forward link slots. The return linkslots may be based on a less spectrally efficient modulation and/orprotocol such as the GPRS (GMSK) modulation and/or protocol. The EDGEmodulation/protocol and the GPRS modulation/protocol are well known tothose having skill in the art, and need not be described further herein.Given an EDGE forward/GPRS return TDD carrier strategy, up to(384/2)=192 kbps may be supported on the forward link while on thereturn link the radiotelephone may transmit at up to (115/2)≈64 kbps.

[0055] In other embodiments, it also is possible to allocate six timeslots of an eight-slot frame for the forward link and only two for thereturn link. In these embodiments, for voice services, given thestatistically symmetric nature of voice, the return link vocoder mayneed to be comparable with quarter-rate GSM, while the forward linkvocoder can operate at full-rate GSM, to yield six full-duplex voicecircuits per GSM TDD-mode carrier (a voice capacity penalty of 25%).Subject to this non-symmetrical partitioning strategy, data rates of upto (384)(6/8)=288 kbps may be achieved on the forward link, with up to(115)(2/8)≈32 kbps on the return link.

[0056]FIG. 6 depicts an ATC architecture according to embodiments of theinvention, which can lend itself to automatic configuration between thetwo modes of standard GSM and TDD GSM on command, for example, from aNetwork Operations Center (NOC) via a Base Station Controller (BSC). Itwill be understood that in these embodiments, an antenna 620 cancorrespond to the antenna 140 a of FIGS. 1 and 4, and the remainder ofFIG. 6 can correspond to the electronics system 140 b of FIGS. 1 and 4.If a reconfiguration command for a particular carrier, or set ofcarriers, occurs while the carrier(s) are active and are supportingtraffic, then, via the in-band signaling Fast Associated Control CHannel(FACCH), all affected radiotelephones may be notified to alsoreconfigure themselves and/or switch over to new resources. Ifcarrier(s) are reconfigured from TDD mode to standard mode, automaticreassignment of the carrier(s) to the appropriate standard-mode ATCs,based, for example, on capacity demand and/or reuse pattern can beinitiated by the NOC. If, on the other hand, carrier(s) are reconfiguredfrom standard mode to TDD mode, automatic reassignment to theappropriate TDD-mode ATCs can take place on command from the NOC.

[0057] Still referring to FIG. 6, a switch 610 may remain closed whencarriers are to be demodulated in the standard mode. In TDD mode, thisswitch 610 may be open during the first half of the frame, when the ATCis transmitting, and closed during the second half of the frame, whenthe ATC is receiving. Other embodiments also may be provided.

[0058]FIG. 6 assumes N transceivers per ATC sector, where N can be assmall as one, since a minimum of one carrier per sector generally isdesired. Each transceiver is assumed to operate over one GSM carrierpair (when in standard mode) and can thus support up to eightfull-duplex voice circuits, neglecting BCCH channel overhead. Moreover,a standard GSM carrier pair can support sixteen full-duplex voicecircuits when in half-rate GSM mode, and up to thirty two full-duplexvoice circuits when in quarter-rate GSM mode.

[0059] When in TDD mode, the number of full duplex voice circuits may bereduced by a factor of two, assuming the same vocoder. However, in TDDmode, voice service can be offered via the half-rate GSM vocoder withalmost imperceptible quality degradation, in order to maintain invariantvoice capacity. FIG. 7 is a block diagram of a reconfigurableradiotelephone architecture that can communicate with a reconfigurableATC architecture of FIG. 6. In FIG. 7, an antenna 720 is provided, andthe remainder of FIG. 7 can provide embodiments of an electronics systemfor the radiotelephone.

[0060] It will be understood that the ability to reconfigure ATCs andradiotelephones according to embodiments of the invention may beobtained at a relatively small increase in cost. The cost may be mostlyin Non-Recurring Engineering (NRE) cost to develop software. Somerecurring cost may also be incurred, however, in that at least anadditional RF filter and a few electronically controlled switches may beused per ATC and radiotelephone. All other hardware/software can becommon to standard-mode and TDD-mode GSM.

[0061] Referring now to FIG. 8, other radiotelephone systems and methodsaccording to embodiments of the invention now will be described. Inthese embodiments, the modified second range of satellite band forwardlink frequencies includes a plurality of frequencies in the second rangeof satellite band forward link frequencies that are transmitted by theATCs to the radiotelephones at a power level, such as maximum powerlevel, that monotonically decreases as a function of (increasing)frequency. More specifically, as will be described below, in someembodiments, the modified second range of satellite band forward linkfrequencies includes a subset of frequencies proximate to a first orsecond end of the range of satellite band forward link frequencies thatare transmitted by the ATC to the radiotelephones at a power level, suchas a maximum power level, that monotonically decreases toward the firstor second end of the second range of satellite band forward linkfrequencies. In still other embodiments, the first range of satelliteband return link frequencies is contained in an L-band of satellitefrequencies above GPS frequencies and the second range of satellite bandforward link frequencies is contained in the L-band of satellitefrequencies below the GPS frequencies. The modified second range ofsatellite band forward link frequencies includes a subset of frequenciesproximate to an end of the second range of satellite band forward linkfrequencies adjacent the GPS frequencies that are transmitted by the ATCto the radiotelephones at a power level, such as a maximum power level,that monotonically decreases toward the end of the second range ofsatellite band forward link frequencies adjacent the GPS frequencies.

[0062] Without being bound by any theory of operation, a theoreticaldiscussion of the mapping of ATC maximum power levels to carrierfrequencies according to embodiments of the present invention now willbe described. Referring to FIG. 8, let ν=

(ρ) represent a mapping from the power (ρ) domain to the frequency (ν)range. The power (ρ) is the power that an ATC uses or should transmit inorder to reliably communicate with a given radiotelephone. This powermay depend on many factors such as the radiotelephone's distance fromthe ATC, the blockage between the radiotelephone and the ATC, the levelof multipath fading in the channel, etc., and as a result, will, ingeneral, change as a function of time. Hence, the power used generallyis determined adaptively (iteratively) via closed-loop power control,between the radiotelephone and ATC.

[0063] The frequency (ν) is the satellite carrier frequency that the ATCuses to communicate with the radiotelephone. According to embodiments ofthe invention, the mapping

is a monotonically decreasing function of the independent variable ρ.Consequently, in some embodiments, as the maximum ATC power increases,the carrier frequency that the ATC uses to establish and/or maintain thecommunications link decreases. FIG. 8 illustrates an embodiment of apiece-wise continuous monotonically decreasing (stair-case) function.Other monotonic functions may be used, including linear and/ornonlinear, constant and/or variable decreases. FACCH or Slow AssociatedControl CHannel (SACCH) messaging may be used in embodiments of theinvention to facilitate the mapping adaptively and in substantially realtime.

[0064]FIG. 9 depicts an ideal cell according to embodiments of theinvention, where, for illustration purposes, three power regions andthree associated carrier frequencies (or carrier frequency sets) arebeing used to partition a cell. For simplicity, one ATC transmitter atthe center of the idealized cell is assumed with no sectorization. Inembodiments of FIG. 9, the frequency (or frequency set) f_(I) is takenfrom substantially the upper-most portion of the L-band forward linkfrequency set, for example from substantially close to 1559 Mhz (seeFIG. 3). Correspondingly, the frequency (or frequency set) f_(M) istaken from substantially the central portion of the L-band forward linkfrequency set (see FIG. 3). In concert with the above, the frequency (orfrequency set) f_(O) is taken from substantially the lowest portion ofthe L-band forward link frequencies, for example close to 1525 Mhz (seeFIG. 3).

[0065] Thus, according to embodiments of FIG. 9, if a radiotelephone isbeing served within the outer-most ring of the cell, that radiotelephoneis being served via frequency f_(O). This radiotelephone, being withinthe furthest area from the ATC, has (presumably) requested maximum (ornear maximum) power output from the ATC. In response to the maximum (ornear maximum) output power request, the ATC uses its a priori knowledgeof power-to-frequency mapping, such as a three-step staircase functionof FIG. 9. Thus, the ATC serves the radiotelephone with a low-valuefrequency taken from the lowest portion of the mobile L-band forwardlink frequency set, for example, from as close to 1525 Mhz as possible.This, then, can provide additional safeguard to any GPS receiver unitthat may be in the vicinity of the ATC.

[0066] Embodiments of FIG. 9 may be regarded as idealized because theyassociate concentric ring areas with carrier frequencies (or carrierfrequency sets) used by an ATC to serve its area. In reality, concentricring areas generally will not be the case. For example, a radiotelephonecan be close to the ATC that is serving it, but with significantblockage between the radiotelephone and the ATC due to a building. Thisradiotelephone, even though relatively close to the ATC, may alsorequest maximum (or near maximum) output power from the ATC. With thisin mind, FIG. 10 may depict a more realistic set of area contours thatmay be associated with the frequencies being used by the ATC to serveits territory, according to embodiments of the invention. The frequency(or frequency set) f_(I) may be reused in the immediately adjacent ATCcells owing to the limited geographical span associated with f_(I)relative to the distance between cell centers. This may also hold forf_(M).

[0067] Referring now to FIG. 11, other modified second ranges ofsatellite band forward link frequencies that can be used by ATCsaccording to embodiments of the present invention now will be described.In these embodiments, at least one frequency in the modified secondrange of satellite band forward link frequencies that is transmitted bythe ATC to the radiotelephones comprises a frame including a pluralityof slots. In these embodiments, at least two contiguous slots in theframe that is transmitted by the ATC to the radiotelephones are leftunoccupied. In other embodiments, three contiguous slots in the framethat is transmitted by the ATC to the radiotelephones are leftunoccupied. In yet other embodiments, at least two contiguous slots inthe frame that is transmitted by the ATC to the radiotelephones aretransmitted at lower power than remaining slots in the frame. In stillother embodiments, three contiguous slots in the frame that istransmitted by the ATC to the radiotelephones are transmitted at lowerpower than remaining slots in the frame. In yet other embodiments, thelower power slots may be used with first selected ones of theradiotelephones that are relatively close to the ATC and/or areexperiencing relatively small signal blockage, and the remaining slotsare transmitted at higher power to second selected ones of theradiotelephones that are relatively far from the ATC and/or areexperiencing relatively high signal blockage.

[0068] Stated differently, in accordance with some embodiments of theinvention, only a portion of the TDMA frame is utilized. For example,only the first four (or last four, or any contiguous four) time slots ofa full-rate GSM frame are used to support traffic. The remaining slotsare left unoccupied (empty). In these embodiments, capacity may be lost.However, as has been described previously, for voice services, half-rateand even quarter-rate GSM may be invoked to gain capacity back, withsome potential degradation in voice quality. The slots that are notutilized preferably are contiguous, such as slots 0 through 3 or 4through 7 (or 2 through 5, etc.). The use of non-contiguous slots suchas 0, 2, 4, and 6, for example, may be less desirable. FIG. 11illustrates four slots (4-7) being used and four contiguous slots (0-3)being empty in a GSM frame.

[0069] It has been found experimentally, according to these embodimentsof the invention, that GPS receivers can perform significantly betterwhen the interval between interference bursts is increased or maximized.Without being bound by any theory of operation, this effect may be dueto the relationship between the code repetition period of the GPS C/Acode (1 msec.) and the GSM burst duration (about 0.577 msec.). With aGSM frame occupancy comprising alternate slots, each GPS signal codeperiod can experience at least one “hit”, whereas a GSM frame occupancycomprising four to five contiguous slots allows the GPS receiver toderive sufficient clean information so as to “flywheel” through theerror events.

[0070] According to other embodiments of the invention, embodiments ofFIGS. 8-10 can be combined with embodiments of FIG. 11. Furthermore,according to other embodiments of the invention, if an f_(I) carrier ofFIGS. 9 or 10 is underutilized, because of the relatively smallfootprint of the inner-most region of the cell, it may be used tosupport additional traffic over the much larger outermost region of thecell.

[0071] Thus, for example, assume that only the first four slots in eachframe of f_(I) are being used for inner region traffic. In embodimentsof FIGS. 8-10, these four f_(I) slots are carrying relatively low powerbursts, for example of the order of 100 mW or less, and may, therefore,appear as (almost) unoccupied from an interference point of view.Loading the remaining four (contiguous) time slots of f_(I) withrelatively high-power bursts may have negligible effect on a GPSreceiver because the GPS receiver would continue to operate reliablybased on the benign contiguous time interval occupied by the fourlow-power GSM bursts. FIG. 12 illustrates embodiments of a frame atcarrier f_(I) supporting four low-power (inner interval) users and fourhigh-power (outer interval) users. In fact, embodiments illustrated inFIG. 12 may be a preferred strategy for the set of available carrierfrequencies that are closest to the GPS band. These embodiments mayavoid undue capacity loss by more fully loading the carrier frequencies.

[0072] The experimental finding that interference from GSM carriers canbe relatively benign to GPS receivers provided that no more than, forexample, 5 slots per 8 slot GSM frame are used in a contiguous fashioncan be very useful. It can be particularly useful since thisexperimental finding may hold even when the GSM carrier frequency isbrought very close to the GPS band (as close as 1558.5 Mhz) and thepower level is set relatively high. For example, with five contiguoustime slots per frame populated, the worst-case measured GPS receiver mayattain at least 30 dB of desensitization margin, over the entire ATCservice area, even when the ATC is radiating at 1558.5 Mhz. With fourcontiguous time slots per frame populated, an additional 10 dBdesensitization margin may be gained for a total of 40 dB for theworst-case measured GPS receiver, even when the ATC is radiating at1558.5 Mhz.

[0073] There still may be concern about the potential loss in networkcapacity (especially in data mode) that may be incurred over thefrequency interval where embodiments of FIG. 11 are used tounderpopulate the frame. Moreover, even though embodiments of FIG. 12can avoid capacity loss by fully loading the carrier, they may do sosubject to the constraint of filling up the frame with both low-powerand high-power users. Moreover, if forward link carriers are limited to5 contiguous high power slots per frame, the maximum forward link datarate per carrier that may be aimed at a particular user, may becomeproportionately less.

[0074] Therefore, in other embodiments, carriers which are subject tocontiguous empty/low power slots are not used for the forward link.Instead, they are used for the return link. Consequently, in someembodiments, at least part of the ATC is configured in reverse frequencymode compared to the SBC in order to allow maximum data rates over theforward link throughout the entire network. On the reverse frequencyreturn link, a radiotelephone may be limited to a maximum of 5 slots perframe, which can be adequate for the return link. Whether the fiveavailable time slots per frame, on a reverse frequency return linkcarrier, are assigned to one radiotelephone or to five differentradiotelephones, they can be assigned contiguously in these embodiments.As was described in connection with FIG. 12, these five contiguous slotscan be assigned to high-power users while the remaining three slots maybe used to serve low-power users.

[0075] Other embodiments may be based on operating the ATC entirely inreverse frequency mode compared to the SBC. In these embodiments, an ATCtransmits over the satellite return link frequencies whileradiotelephones respond over the satellite forward link frequencies. Ifsufficient contiguous spectrum exists to support CDMA technologies, andin particular the emerging Wideband-CDMA 3G standard, the ATC forwardlink can be based on Wideband-CDMA to increase or maximize datathroughput capabilities. Interference with GPS may not be an issue sincethe ATCs transmit over the satellite return link in these embodiments.Instead, interference may become a concern for the radiotelephones.Based, however, on embodiments of FIGS. 11-12, the radiotelephones canbe configured to transmit GSM since ATC return link rates are expected,in any event, to be lower than those of the forward link. Accordingly,the ATC return link may employ GPRS-based data modes, possibly evenEDGE. Thus, return link carriers that fall within a predeterminedfrequency interval from the GPS band-edge of 1559 Mhz, can be underloaded, per embodiments of FIGS. 11 or 12, to satisfy GPS interferenceconcerns.

[0076] Finally, other embodiments may use a partial or total reversefrequency mode and may use CDMA on both forward and return links. Inthese embodiments, the ATC forward link to the radiotelephones utilizesthe frequencies of the satellite return link (1626.5 Mhz to 1660.5 Mhz)whereas the ATC return link from the radiotelephones uses thefrequencies of the satellite forward link (1525 Mhz to 1559 Mhz). TheATC forward link can be based on an existing or developing CDMAtechnology (e.g., IS-95, Wideband-CDMA, etc.). The ATC network returnlink can also be based on an existing or developing CDMA technologyprovided that the radiotelephone's output is gated to ceasetransmissions for approximately 3 msec once every T msec. In someembodiments, T will be greater than or equal to 6 msec.

[0077] This gating may not be needed for ATC return link carriers atapproximately 1550 Mhz or below. This gating can reduce or minimizeout-of-band interference (desensitization) effects for GPS receivers inthe vicinity of an ATC. To increase the benefit to GPS, the gatingbetween all radiotelephones over an entire ATC service area can besubstantially synchronized. Additional benefit to GPS may be derivedfrom system-wide synchronization of gating. The ATCs can instruct allactive radiotelephones regarding the gating epoch. All ATCs can bemutually synchronized via GPS.

[0078] Spatial Guardbands for Terrestrial Reuse of Satellite Frequencies

[0079] Some embodiments of the invention that were described above inconnection with FIGS. 1-2 included interference reducers, to allow asatellite radiotelephone frequency to be reused terrestrially within thesame satellite cell, while allowing intra-system interference to bereduced or eliminated. Embodiments of the invention that will now bedescribed in connection with FIGS. 13 and 14 can allow a satelliteradiotelephone frequency for a given satellite cell to be reusedterrestrially outside the given satellite cell. Some embodiments providea spatial guardband that is sufficiently large to reduce or preventinterference between the satellite frequencies that are used forspace-based communications in the given satellite cell and reusedterrestrially outside the given cell. In other embodiments, the spatialguardband may not need to be used, in whole or in part.

[0080] Spatial guardbands according to some embodiments of the inventionmay be provided by separating the ancillary terrestrial components inthe ancillary terrestrial network that terrestrially reuse the same (ornearby) frequency or frequencies as the given satellite radiotelephonecell outside a given (predetermined) satellite radiotelephone cell, by asufficient distance from the given satellite radiotelephone cell, suchthat signals are attenuated to some desired degree by the satellite'santenna pattern. For example, the signals are attenuated such thattransmissions from the ancillary terrestrial components that radiate thefrequency or frequencies that are used in the given satelliteradiotelephone cell are sufficiently attenuated in the given satellitecell, so as to reduce or prevent (harmful) interference therewith.

[0081] By providing a spatial guardband, some terrestrial reuse ofsatellite frequencies may be obtained. Moreover, an interferencereducer, such as the interference reducer of FIGS. 1 or 2, may not needto be used. The complexity of the system therefore may be reduced.Alternatively, when interference reducers according to embodiments ofthe invention are used, a satellite radiotelephone frequency also can beused terrestrially within the very same satellite cell, with reduced orno interference, but at the potential expense of system complexity.

[0082] Qualitatively, embodiments of the present invention that providea spatial guardband for terrestrial reuse of satellite frequencies mayuse a predetermined frequency or set of frequencies for space-basedcommunications within a given satellite radiotelephone cell. Accordingto these embodiments, this frequency or set of frequencies is not reusedterrestrially within the given satellite radiotelephone cell, by theancillary terrestrial network. However, the ancillary terrestrialnetwork that exists outside the given satellite radiotelephone cell canreuse this frequency or set of frequencies, as long as a spatialguardband is maintained around the given satellite radiotelephone cellthat uses this frequency or set of frequencies for space-basedcommunications.

[0083]FIG. 13 is a schematic diagram of a satellite cellularradiotelephone system that uses a seven-cell frequency reuse pattern,wherein an ancillary terrestrial network reuses the satellitefrequencies with the provision of a spatial guardband. Thus, FIG. 13illustrates a seven-cell frequency reuse pattern 1310, outlined in athick line, with satellite cells 1-7 contained within the seven-cellfrequency reuse pattern. Although only eight repetitions of thefrequency reuse plan 1310 are shown in FIG. 13, fewer or morerepetitions may be used.

[0084] As is well known to those having skill in the art, a satellitecell, such as cells 1-7 of FIG. 13, may have a diameter that is on theorder of hundreds of kilometers. In sharp contrast, a terrestrialnetwork cell, such as a cell of an ancillary terrestrial network, mayhave a cell diameter that is on the order of ten kilometers or less.Thus, within a given satellite cell, such as a satellite cell 1-7 ofFIG. 13, on the order of hundreds or thousands of ancillary terrestrialnetwork cells may be present. As was shown in FIG. 1, each ancillaryterrestrial network cell may include at least one ancillary terrestrialcomponent (e.g., a base station tower with associate electronics).

[0085] According to some embodiments of the invention, selected ones ofthe ancillary terrestrial network cells outside a given satelliteradiotelephone cell, such as cell 1 of FIG. 13, may terrestrially reusethe frequency or frequencies that are used by the given satelliteradiotelephone cell 1, as long as those ancillary terrestrial networkcells are spatially separated from the given satellite cell 1 by aguardband GB of FIG. 13 which is sufficiently large to reduce or preventinterference with the same frequency or frequencies that are also usedin the given satellite radiotelephone cell 1. Although the guardband GBof FIG. 13 is shown as a symmetrical ring, realworld guardbands may havean irregular shape to account for the actual satellite antenna patternswhich may intentionally or unintentionally deviate from those shown inFIG. 13.

[0086] Thus, as shown in FIG. 13 by the hatched area outside thesatellite radiotelephone cells 1, ancillary terrestrial componentswithin the ancillary terrestrial network in the hatched portions ofsatellite radiotelephone cells 2-7 can include an electronics systemassociated therewith, which can be configured to terrestrially reuse thesame satellite frequency or frequencies used by cell 1, as long as asufficient spatial guardband, shown by the unhatched areas of FIG. 13,is maintained between satellite cells 1 and the ancillary terrestrialcomponents that terrestrially reuse these frequencies. The guardband maybe on the order of half the radius of a satellite cell in width, but mayvary based upon the actual design of the system. Stated differently, agiven frequency or set of frequencies may be used throughout the hatchedand cross-hatched area of FIG. 13, with the frequencies being used forspace-based communications in the cross-hatched portions, correspondingto satellite cells 1, and also reused terrestrially in the hatchedportions of the ancillary terrestrial network that are spatiallyseparated from the satellite cells 1 by the guardband GB.

[0087] It will be understood by those having skill in the art thatsimilar terrestrial reuse of satellite frequencies with spatialguardbands may be provided for the frequency or frequencies that areused in each of the remaining satellite cells 2-7. Terrestrial reusewith a spatial guardband for cells 2-7 are not shown in FIG. 13 for thesake of clarity.

[0088]FIG. 14 illustrates other examples of terrestrial reuse ofsatellite frequencies using spatial guardbands according to someembodiments of the invention. In FIG. 14, a nine-cell frequency reusepattern 1410 is shown for satellite radiotelephone cells 1-9. As alsoshown in FIG. 14, the frequency or frequencies that are used by a givensatellite radiotelephone cell, for example cells 5, may be reused in theancillary terrestrial network that overlaps with the remaining satellitecells 1-4 and 6-9, as long as a sufficient guardband GB is maintained,to reduce or prevent interference. As was the case for FIG. 13,terrestrial reuse of satellite frequencies with a spatial guardband isonly shown for the frequency or frequencies used in satellite cells 5.The frequencies for the remaining satellite cells 1-4 and 6-9 also maybe reused terrestrially in a similar manner, but are not shown in FIG.14 for the sake of clarity.

[0089] As was described above, in some embodiments of the presentinvention, an ancillary terrestrial network is configured toterrestrially reuse at least one of the satellite radiotelephonefrequencies that is used in a predetermined satellite cell in thesatellite footprint, outside the predetermined satellite cell andseparated therefrom by a spatial guardband. In some embodiments, whenthe ancillary terrestrial network comprises a plurality of ancillaryterrestrial components, at least a first one of the ancillaryterrestrial components that is located in the predetermined satellitecell is configured not to terrestrially reuse the at least one of thesatellite radiotelephone frequencies that is used in the predeterminedsatellite cell, and at least a second of the ancillary terrestrialcomponents that is located outside the predetermined satellite cell andseparated therefrom by the spatial guardband, is configured toterrestrially reuse the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell.Accordingly, it may be desirable to determine, for each ancillaryterrestrial component, whether the ancillary terrestrial component islocated outside the predetermined satellite cell and separated therefromby a spatial guardband.

[0090] In some embodiments of the invention, this determination may bemade, for example at the time of setup of the ancillary terrestrialcomponent, based on the geographic location thereof. Moreover, thedetermination also may be updated or changed by receiving a message atthe ancillary terrestrial component that indicates that its locationrelative to the predetermined satellite cell has changed. This updatemay be used, for example, when the location of the satellite cells inthe satellite footprint changes.

[0091] It may be difficult and/or time consuming to determine theboundaries (signal strength contours) of the spatial guardband regionswith sufficient accuracy. Moreover, the satellite antenna pattern maydrift over time. Also, the satellite antenna pattern may be reconfiguredperiodically. Accordingly, other embodiments of the present inventionmay be configured to determine portions of the ancillary terrestrialnetwork that are located outside the predetermined satellite cell andseparated therefrom by a spatial guardband. In some embodiments, thisdetermination may be made by receiving and/or processing at least one ofthe satellite radiotelephone frequencies of the satellite telephonefrequency band. In still other embodiments, the satellite telephonefrequencies include a plurality of Broadcast Control CHannel (BCCH)frequencies, and the determination is made by receiving and/orprocessing signal strength and/or content of at least one of the BCCHfrequencies.

[0092] In still other embodiments, the ancillary terrestrial networkcomprises a plurality of ancillary terrestrial components. In someembodiments, each of these ancillary terrestrial components can beconfigured to determine whether it is located outside the predeterminedsatellite cell and separated therefrom by the spatial guardband.Moreover, in other embodiments, not every ancillary terrestrialcomponent needs to determine whether it is located outside thepredetermined satellite cell and separated therefrom by the spatialguardband. Rather, in these embodiments, at least one of the ancillaryterrestrial components is configured to determine whether it is locatedoutside the predetermined satellite cell and separated therefrom by aspatial guardband, and to transmit results of this determination to atleast a second one of the plurality of ancillary terrestrial components.Accordingly, the ancillary terrestrial components can determine thesatellite band frequencies that they may deploy.

[0093] More specifically, an ancillary terrestrial component may beequipped to receive the BCCH carrier frequencies that the satellitesystem is radiating. For example, for a seven cell frequency reusepattern such as illustrated in FIG. 13, seven distinct carrierfrequencies may be used by the satellite system for BCCH transmissions.These frequencies may be known a priori by the ancillary terrestrialnetwork. The ancillary terrestrial components may be configured toreceive and demodulate the BCCH carrier frequencies eithersimultaneously or sequentially.

[0094] Each satellite BCCH carrier, corresponding to a particularsatellite cell, may contain information revealing frequencies (carriers)that the satellite cell is using for communications traffic. Thesatellite BCCH carrier also may carry information revealing the totalset of frequencies available to the satellite system, as well as thefrequency sets available for communications to other neighboring cellscorresponding to the carriers used for BCCH transmission by the otherneighboring (adjacent) satellite cells.

[0095] According to some embodiments of the present invention, since theancillary terrestrial component is able to receive and demodulate theBCCH carrier frequencies used by the satellite system, it can determinethe relative strengths of the received satellite BCCH carriers and theset of frequencies assigned for communications corresponding to eachreceived BCCH carrier. Thus, with real time knowledge of the satellitesystem state and the received BCCH carrier strengths, an ancillaryterrestrial component may not need to obtain additional informationregarding its own position relative to any one spatial guardband and theassociated boundaries (signal strength contours) thereof.

[0096] It will be understood by those having skill in the art that thearea that may be spanned by ancillary terrestrial components generallymay be relatively small compared to the regions spanned by satellitecells and/or spatial guardbands, in some embodiments. As such, accordingto other embodiments of the present invention, not every ancillaryterrestrial component may need to be equipped with the satellite BCCHreception. In particular, only one or a few ancillary terrestrialcomponents per satellite cell may need to detect the satellite BCCH. Infact, the detection of the satellite BCCH carrier frequencies may noteven be collocated with any ancillary terrestrial component. Thus, onlyone or a subset of the ancillary terrestrial components that provideservice to a geographical area may need to determine the frequency setthat it may use for communications, and then can transmit thisinformation to other ancillary terrestrial components serving thegeographic area.

[0097] In some embodiments, in response to the received signal levelsand/or the information content of the satellite BCCH carriers, theancillary terrestrial component serving a given geographic area, or asubset of the ancillary terrestrial components, can determine thesatellite band frequencies that they may deploy with reduced or minimuminterference impact to the satellite communications. In someembodiments, satellite band frequencies that are associated with theweakest satellite BCCH carrier that is received, may be deployed by theancillary terrestrial components with highest priority, following bythose corresponding to the next weakest BCCH carrier, etc. Thus, theentire ancillary terrestrial network that may be serving a particulargeographic area may configure and reconfigure its frequency plan and, insome embodiments, in real time, in response to monitoring of thesatellite network BCCH emissions.

[0098] Embodiments of the invention as illustrated, for example, inFIGS. 13 and 14 can terrestrially reuse satellite frequencies over muchof the ancillary terrestrial network, and some embodiments can rely onspatial guardbands to reduce or prevent interference. Interferencereducers, for example as shown in FIGS. 1-2, may not need to be used.However, it also will be understood that other embodiments may use acombination of terrestrial reuse using a spatial guardband andterrestrial reuse using an interference reducer over different portionsof the satellite radiotelephone system footprint.

[0099] Accordingly, some embodiments of the invention can providesatellite radiotelephone systems and methods, wherein a space-basedcomponent is configured to receive wireless communications fromradiotelephones in a satellite footprint over a satellite radiotelephonefrequency band, and an ancillary terrestrial network also is configuredto receive wireless communications from radiotelephones in the satellitefootprint over the satellite radiotelephone frequency band. One or morefrequencies used in a given satellite cell of the satellite footprintalso are used by the ancillary terrestrial network that is outside thegiven satellite cell and, in some embodiments, that is separated fromthe given cell by a predetermined spatial guardband. Terrestrial reusetherefore may be provided over much of the satellite footprint, withoutcreating excessive interference.

[0100] In the drawings and specification, there have been disclosedtypical preferred embodiments of the invention and, although specificterms are employed, they are used in a generic and descriptive senseonly and not for purposes of limitation, the scope of the inventionbeing set forth in the following claims.

What is claimed is:
 1. A satellite radiotelephone system comprising: aspace-based component that is configured to provide wirelessradiotelephone communications in a satellite footprint over a satelliteradiotelephone frequency band, the satellite footprint being dividedinto a plurality of satellite cells in which satellite radiotelephonefrequencies of the satellite radiotelephone frequency band are spatiallyreused; and an ancillary terrestrial network that is configured toterrestrially reuse at least one of the satellite radiotelephonefrequencies that is used in a predetermined satellite cell in thesatellite footprint, outside the predetermined satellite cell.
 2. Asatellite radiotelephone system according to claim 1 wherein theancillary terrestrial network is further configured to terrestriallyreuse at least one of the satellite radiotelephone frequencies that isused in a predetermined satellite cell in the satellite footprint,outside the predetermined satellite cell and separated therefrom by aspatial guardband.
 3. A satellite radiotelephone system according toclaim 2 wherein the spatial guardband is sufficiently large to reduceinterference between the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint, and the at least one of the satelliteradiotelephone frequencies that is terrestrially reused outside thepredetermined satellite cell and separated therefrom by the spatialguardband.
 4. A satellite radiotelephone system according to claim 2wherein the spatial guardband is sufficiently large to preventinterference between the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint, and the at least one of the satelliteradiotelephone frequencies that is terrestrially reused outside thepredetermined satellite cell and separated therefrom by the spatialguardband.
 5. A satellite radiotelephone system according to claim 2wherein the ancillary terrestrial network is configured to terrestriallyreuse at least one of the satellite radiotelephone frequencies that isused in the predetermined satellite cell in the satellite footprint,outside the predetermined satellite cell and separated therefrom by thespatial guardband by receiving the at least one of the satelliteradiotelephone frequencies that is used in the predetermined satellitecell in the satellite footprint, outside the predetermined satellitecell and separated therefrom by the spatial guardband.
 6. A satelliteradiotelephone system according to claim 2 wherein the ancillaryterrestrial network is configured to terrestrially reuse at least one ofthe satellite radiotelephone frequencies that is used in thepredetermined satellite cell in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband by receiving the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint and at least one other frequency that is used by thespace-based component in the satellite footprint, outside thepredetermined satellite cell and separate therefrom by the spatialguardband.
 7. A satellite radiotelephone system according to claim 2wherein the ancillary terrestrial network is configured to terrestriallyreuse at least one of the satellite radiotelephone frequencies that isused in the predetermined satellite cell in the satellite footprint,outside the predetermined satellite cell and separated therefrom by thespatial guardband by transmitting the at least one of the satelliteradiotelephone frequencies that is used in the predetermined satellitecell in the satellite footprint, outside the predetermined satellitecell and separated therefrom by the spatial guardband.
 8. A satelliteradiotelephone system according to claim 2 wherein the ancillaryterrestrial network is configured to terrestrially reuse at least one ofthe satellite radiotelephone frequencies that is used in thepredetermined satellite cell in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband by transmitting the at least one of the satelliteradiotelephone frequencies that is used in the predetermined satellitecell in the satellite footprint and at least one other frequency that isused by the space-based component in the satellite footprint, outsidethe predetermined satellite cell and separated therefrom by the spatialguardband.
 9. A satellite radiotelephone system according to claim 2wherein the spatial guardband is about half a radius of a satellite cellin width.
 10. A satellite radiotelephone system according to claim 1further comprising: an interference reducer that is responsive to thespace-based component and to the ancillary terrestrial network, and thatis configured to reduce interference from wireless communications thatare received by the space-based component from a first radiotelephone inthe satellite footprint over the satellite radiotelephone frequencyband, using wireless communications that are received by the ancillaryterrestrial network from a second radiotelephone in the satellitefootprint over the satellite radiotelephone frequency band.
 11. Asatellite radiotelephone system according to claim 2: wherein theancillary terrestrial network is divided into a plurality of ancillaryterrestrial network cells in which frequencies of the satelliteradiotelephone frequency band are spatially reused and is furtherconfigured to terrestrially reuse at least one of the satelliteradiotelephone frequencies that is used in a predetermined satellitecell in the satellite footprint, in ancillary terrestrial network cellsthat are outside the predetermined satellite cell and separatedtherefrom by the spatial guardband.
 12. A satellite radiotelephonesystem according to claim 2: wherein the ancillary terrestrial networkis further configured to terrestrially reuse at least one of thesatellite radiotelephone frequencies that is used in the predeterminedsatellite cell in the satellite footprint, by not terrestrially reusingthe at least one of the satellite radiotelephone frequencies that isused in the predetermined satellite cell in the satellite footprint,within the predetermined satellite cell or within the spatial guardband.13. A satellite radiotelephone system according to claim 2 wherein theancillary terrestrial network comprises a plurality of ancillaryterrestrial components, at least a first one of which is located in thepredetermined satellite cell and is configured not to terrestriallyreuse the at least one of the satellite radiotelephone frequencies thatis used in the predetermined satellite cell for satellitecommunications, and at least a second one of which is located outsidethe predetermined satellite cell and separated therefrom by the spatialguardband and is configured to terrestrially reuse the at least one ofthe satellite radiotelephone frequencies that is used in thepredetermined satellite cell for satellite communications.
 14. Asatellite radiotelephone system according to claim 1 in combination witha plurality of radiotelephones that are configured to wirelesslycommunicate with the space-based component and/or the ancillaryterrestrial network.
 15. A satellite radiotelephone system according toclaim 2 wherein the ancillary terrestrial network is further configuredto determine portions thereof that are located outside the predeterminedsatellite cell and separated therefrom by the spatial guardband.
 16. Asatellite radiotelephone system according to claim 15 wherein theancillary terrestrial network is further configured to determine whetherportions thereof are located outside the predetermined satellite celland separated therefrom by the spatial guardband by receiving and/orprocessing at least one of the satellite radiotelephone frequencies ofthe satellite radiotelephone frequency band.
 17. A satelliteradiotelephone system according to claim 15 wherein the satelliteradiotelephone frequencies include a plurality of Broadcast ControlCHannel (BCCH) frequencies and wherein the ancillary terrestrial networkis further configured to determine portions thereof that are locatedoutside the predetermined satellite cell and separated therefrom by thespatial guardband by receiving and/or processing signal strength and/orcontent of at least one of the BCCH frequencies.
 18. A satelliteradiotelephone system according to claim 15 wherein the ancillaryterrestrial network comprises a plurality of ancillary terrestrialcomponents, each of which is configured to determine whether it islocated outside the predetermined satellite cell and separated therefromby the spatial guardband.
 19. A satellite radiotelephone systemaccording to claim 15 wherein the ancillary terrestrial networkcomprises a plurality of ancillary terrestrial components, at least oneof which is configured to determine whether it is located outside thepredetermined satellite cell and separated therefrom by the spatialguardband and to transmit results of the determination to at least asecond one of the plurality of ancillary terrestrial components.
 20. Anancillary terrestrial component for a satellite radiotelephone systemthat includes a space-based component that is configured to providewireless radiotelephone communications in a satellite footprint over asatellite radiotelephone frequency band, the satellite footprint beingdivided into a plurality of satellite cells in which satelliteradiotelephone frequencies of the satellite radiotelephone frequencyband are spatially reused, the ancillary terrestrial componentcomprising: an electronics system that is configured to terrestriallyreuse at least one of the satellite radiotelephone frequencies that isused in at least one predetermined satellite cell in the satellitefootprint when the ancillary terrestrial component is located outsidethe at least one predetermined satellite cell and not to terrestriallyreuse the at least one of the satellite radiotelephone frequencies thatis used in the predetermined satellite cell in the satellite footprintwhen the ancillary terrestrial component is located within thepredetermined satellite cell.
 21. An ancillary terrestrial componentaccording to claim 20 wherein the electronics system is furtherconfigured to terrestrially reuse at least one of the satelliteradiotelephone frequencies that is used in at least one predeterminedsatellite cell in the satellite footprint when the ancillary terrestrialcomponent is located outside the at least one predetermined satellitecell an separated therefrom by a spatial guardband and not toterrestrially reuse the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint when the ancillary terrestrial component is locatedwithin the predetermined satellite cell or within the spatial guardband.22. An ancillary terrestrial component according to claim 21 wherein thespatial guardband is sufficiently large to reduce interference betweenthe at least one of the satellite radiotelephone frequencies that isused in the predetermined satellite cell in the satellite footprint, andthe at least one of the satellite radiotelephone frequencies that isterrestrially reused outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 23. An ancillaryterrestrial component according to claim 21 wherein the spatialguardband is sufficiently large to prevent interference between the atleast one of the satellite radiotelephone frequencies that is used inthe predetermined satellite cell in the satellite footprint, and the atleast one of the satellite radiotelephone frequencies that isterrestrially reused outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 24. An ancillaryterrestrial component according to claim 21 wherein the ancillaryterrestrial component is configured to terrestrially reuse at least oneof the satellite radiotelephone frequencies that is used in thepredetermined satellite cell in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband by receiving the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint, outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 25. An ancillaryterrestrial component according to claim 21 wherein the ancillaryterrestrial component is configured to terrestrially reuse at least oneof the satellite radiotelephone frequencies that is used in thepredetermined satellite cell in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband by receiving the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint and at least one other frequency that is used by thespace-based component in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband.
 26. An ancillary terrestrial component according to claim 21wherein the ancillary terrestrial component is configured toterrestrially reuse at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint, outside the predetermined satellite cell andseparated therefrom by the spatial guardband by transmitting the atleast one of the satellite radiotelephone frequencies that is used inthe predetermined satellite cell in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband.
 27. An ancillary terrestrial component according to claim 21wherein the ancillary terrestrial component is configured toterrestrially reuse at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint, outside the predetermined satellite cell andseparated therefrom by the spatial guardband by transmitting the atleast one of the satellite radiotelephone frequencies that is used inthe predetermined satellite cell in the satellite footprint and at leastone other frequency that is used by the space-based component in thesatellite footprint, outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 28. An ancillaryterrestrial component according to claim 21 wherein the spatialguardband is about half a radius of a satellite cell in width.
 29. Anancillary terrestrial component according to claim 20 in combinationwith a plurality of radiotelephones that are configured to wirelesslycommunicate with the space-based component and/or the ancillaryterrestrial component.
 30. An ancillary terrestrial component accordingto claim 21 wherein the ancillary terrestrial component is furtherconfigured to determine whether the ancillary terrestrial component islocated outside the predetermined satellite cell and separated therefromby the spatial guardband.
 31. An ancillary terrestrial componentaccording to claim 30 wherein the ancillary terrestrial component isfurther configured to determine whether the ancillary terrestrialcomponent is located outside the predetermined satellite cell andseparated therefrom by the spatial guardband by receiving and/orprocessing at least one of the satellite radiotelephone frequencies ofthe satellite radiotelephone frequency band.
 32. An ancillaryterrestrial component according to claim 30 wherein the satelliteradiotelephone frequencies include a plurality of Broadcast ControlCHannel (BCCH) frequencies and wherein the ancillary terrestrialcomponent is further configured to determine whether the ancillaryterrestrial component is located outside the predetermined satellitecell and separated therefrom by the spatial guardband by receivingand/or processing signal strength and/or content of at least one of theBCCH frequencies.
 33. An ancillary terrestrial component according toclaim 30 wherein the ancillary terrestrial component is configured todetermine whether it is located outside the predetermined satellite celland separated therefrom by the spatial guardband and to transmit resultsof the determination to at least a second ancillary terrestrialcomponent.
 34. A satellite radiotelephone communications methodcomprising: providing space-based wireless radiotelephone communicationsin a satellite footprint over a satellite radiotelephone frequency band,the satellite footprint being divided into a plurality of satellitecells in which satellite radiotelephone frequencies of the satelliteradiotelephone frequency band are spatially reused; and terrestriallyreusing at least one of the satellite radiotelephone frequencies that isused in a predetermined satellite cell in the satellite footprint,outside the predetermined satellite cell.
 35. A satellite radiotelephonecommunications method according to claim 34 wherein the terrestriallyreusing comprises: terrestrially reusing at least one of the satelliteradiotelephone frequencies that is used in a predetermined satellitecell in the satellite footprint, outside the predetermined satellitecell and separated therefrom by a spatial guardband.
 36. A satelliteradiotelephone communications method according to claim 35 wherein thespatial guardband is sufficiently large to reduce interference betweenthe at least one of the satellite radiotelephone frequencies that isused in the predetermined satellite cell in the satellite footprint, andthe at least one of the satellite radiotelephone frequencies that isterrestrially reused outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 37. A satelliteradiotelephone communications method according to claim 35 wherein thespatial guardband is sufficiently large to prevent interference betweenthe at least one of the satellite radiotelephone frequencies that isused in the predetermined satellite cell in the satellite footprint, andthe at least one of the satellite radiotelephone frequencies that isterrestrially reused outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 38. A satelliteradiotelephone communications method according to claim 35 wherein theterrestrially reusing comprises receiving the at least one of thesatellite radiotelephone frequencies that is used in the predeterminedsatellite cell in the satellite footprint, outside the predeterminedsatellite cell and separated therefrom by the spatial guardband.
 39. Asatellite radiotelephone communications method according to claim 35wherein the terrestrially reusing comprises receiving the at least oneof the satellite radiotelephone frequencies that is used in thepredetermined satellite cell in the satellite footprint and at least oneother frequency that is used by the space-based component in thesatellite footprint, outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 40. A satelliteradiotelephone communications method according to claim 35 wherein theterrestrially reusing comprises transmitting the at least one of thesatellite radiotelephone frequencies that is used in the predeterminedsatellite cell in the satellite footprint, outside the predeterminedsatellite cell and separated therefrom by the spatial guardband.
 41. Asatellite radiotelephone communications method according to claim 35wherein the terrestrially reusing comprises transmitting the at leastone of the satellite radiotelephone frequencies that is used in thepredetermined satellite cell in the satellite footprint and at least oneother frequency that is used by the space-based component in thesatellite footprint, outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 42. A satelliteradiotelephone communications method according to claim 35 wherein thespatial guardband is about half a radius of a satellite cell in width.43. A satellite radiotelephone communications method according to claim34 further comprising: reducing interference from space-based wirelesscommunications that are received from a first radiotelephone in thesatellite footprint over the satellite radiotelephone frequency band,using wireless communications that are received terrestrially from asecond radiotelephone in the satellite footprint over the satelliteradiotelephone frequency band.
 44. A satellite radiotelephonecommunications method according to claim 35 further comprising:refraining from terrestrially reusing the at least one of the satelliteradiotelephone frequencies that is used in the predetermined satellitecell in the satellite footprint, within the predetermined satellite cellor within the spatial guardband.
 45. A satellite radiotelephonecommunications method according to claim 35 further comprisingdetermining where to terrestrially reuse the at least one of thesatellite radiotelephone frequencies that is used in the predeterminedsatellite cell in the satellite footprint.
 46. A satelliteradiotelephone communications method according to claim 45 wherein thedetermining comprises receiving and/or processing at least one of thesatellite radiotelephone frequencies of the satellite radiotelephonefrequency band.
 47. A satellite radiotelephone communications methodaccording to claim 45 wherein the satellite radiotelephone frequenciesinclude a plurality of Broadcast Control CHannel (BCCH) frequencies andwherein the determining comprises receiving and/or processing signalstrength and/or content of at least one of the BCCH frequencies.
 48. Asatellite radiotelephone system according to claim 45 further comprisingtransmitting results of the determining.
 49. A satellite radiotelephonesystem comprising: means for providing space-based wirelessradiotelephone communications in a satellite footprint over a satelliteradiotelephone frequency band, the satellite footprint being dividedinto a plurality of satellite cells in which satellite radiotelephonefrequencies of the satellite radiotelephone frequency band are spatiallyreused; and means for terrestrially reusing at least one of thesatellite radiotelephone frequencies that is used in a predeterminedsatellite cell in the satellite footprint, outside the predeterminedsatellite cell.
 50. A satellite radiotelephone system according to claim49 wherein the means for terrestrially reusing comprises: means forterrestrially reusing at least one of the satellite radiotelephonefrequencies that is used in a predetermined satellite cell in thesatellite footprint, outside the predetermined satellite cell andseparated therefrom by a spatial guardband.
 51. A satelliteradiotelephone system according to claim 50 wherein the spatialguardband is sufficiently large to reduce interference between the atleast one of the satellite radiotelephone frequencies that is used inthe predetermined satellite cell in the satellite footprint, and the atleast one of the satellite radiotelephone frequencies that isterrestrially reused outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 52. A satelliteradiotelephone system according to claim 50 wherein the spatialguardband is sufficiently large to prevent interference between the atleast one of the satellite radiotelephone frequencies that is used inthe predetermined satellite cell in the satellite footprint, and the atleast one of the satellite radiotelephone frequencies that isterrestrially reused outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 53. A satelliteradiotelephone system according to claim 50 wherein the means forterrestrially reusing comprises means for receiving the at least one ofthe satellite radiotelephone frequencies that is used in thepredetermined satellite cell in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband.
 54. A satellite radiotelephone system according to claim 50wherein the means for terrestrially reusing comprises means forreceiving the at least one of the satellite radiotelephone frequenciesthat is used in the predetermined satellite cell in the satellitefootprint and at least one other frequency that is used by the means forproviding in the satellite footprint, outside the predeterminedsatellite cell and separated therefrom by the spatial guardband.
 55. Asatellite radiotelephone system according to claim 50 wherein the meansfor terrestrially reusing comprises means for transmitting the at leastone of the satellite radiotelephone frequencies that is used in thepredetermined satellite cell in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband.
 56. A satellite radiotelephone system according to claim 50wherein the means for terrestrially reusing comprises means fortransmitting the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint and at least one other frequency that is used by themeans for providing in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband.
 57. A satellite radiotelephone system according to claim 50wherein the spatial guardband is about half a radius of a satellite cellin width.
 58. A satellite radiotelephone system according to claim 49further comprising: means for reducing interference from space-basedwireless communications that are received from a first radiotelephone inthe satellite footprint over the satellite radiotelephone frequencyband, using wireless communications that are received terrestrially froma second radiotelephone in the satellite footprint over the satelliteradiotelephone frequency band.
 59. A satellite radiotelephone systemaccording to claim 50: wherein the means for terrestrially reusingcomprises: a plurality of ancillary terrestrial network cells in whichfrequencies of the satellite radiotelephone frequency band are spatiallyreused; and means for terrestrially reusing at least one of thesatellite radiotelephone frequencies that is used in a predeterminedsatellite cell in the satellite footprint, in ancillary terrestrialnetwork cells that are outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 60. A satelliteradiotelephone system according to claim 50: wherein the means forterrestrially reusing further comprises means for refraining fromterrestrially reusing the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint for satellite communications, within thepredetermined satellite cell or within the spatial guardband.
 61. Asatellite radiotelephone system according to claim 50 wherein the meansfor terrestrially reusing comprises a plurality of ancillary terrestrialcomponents, at least a first one of which is located in thepredetermined satellite cell and comprises means for refraining fromterrestrially reusing the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell forsatellite communications, and at least a second one of which is locatedoutside the predetermined satellite cell and separated therefrom by thespatial guardband and comprises means for terrestrially reusing the atleast one of the satellite radiotelephone frequencies that is used inthe predetermined satellite cell for satellite communications.
 62. Asatellite radiotelephone system according to claim 49 in combinationwith a plurality of radiotelephones that are configured to wirelesslycommunicate therewith in space-based and/or the terrestrial modes.
 63. Asatellite radiotelephone system according to claim 49 wherein the meansfor terrestrially reusing comprises means for determining where toterrestrially reuse the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint.
 64. A satellite radiotelephone system according toclaim 63 wherein the means for determining comprises means for receivingand/or processing at least one of the satellite radiotelephonefrequencies of the satellite radiotelephone frequency band.
 65. Asatellite radiotelephone system according to claim 63 wherein thesatellite radiotelephone frequencies include a plurality of BroadcastControl CHannel (BCCH) frequencies and wherein the means for determiningcomprises means for receiving and/or processing signal strength and/orcontent of at least one of the BCCH frequencies.
 66. A satelliteradiotelephone system according to claim 63 wherein the means forterrestrially reusing comprises a plurality of ancillary terrestrialcomponents, each of which comprises means for determining whether it islocated outside the predetermined satellite cell and separated therefromby the spatial guardband.
 67. A satellite radiotelephone systemaccording to claim 63 wherein the means for terrestrially reusingcomprises a plurality of ancillary terrestrial components, at least oneof which comprises means for determining whether it is located outsidethe predetermined satellite cell and separated therefrom by the spatialguardband and means for transmitting results of the means fordetermining to at least a second one of the plurality of ancillaryterrestrial components.
 68. An ancillary terrestrial component for asatellite radiotelephone system that includes a space-based componentthat is configured to provide wireless radiotelephone communications ina satellite footprint over a satellite radiotelephone frequency band,the satellite footprint being divided into a plurality of satellitecells in which satellite radiotelephone frequencies of the satelliteradiotelephone frequency band are spatially reused, the ancillaryterrestrial component comprising: means for terrestrially reusing atleast one of the satellite radiotelephone frequencies that is used in apredetermined satellite cell in the satellite footprint when theancillary terrestrial component is located outside the predeterminedsatellite cell; and means for refraining from terrestrially reusing theat least one of the satellite radiotelephone frequencies that is used inthe predetermined satellite cell in the satellite footprint when theancillary terrestrial component is located within the predeterminedsatellite cell.
 69. An ancillary terrestrial component according toclaim 68: wherein the means for terrestrially reusing comprises meansfor terrestrially reusing at least one of the satellite radiotelephonefrequencies that is used in a predetermined satellite cell in thesatellite footprint when the ancillary terrestrial component is locatedoutside the predetermined satellite cell and separated from therefrom bya spatial guardband; and wherein the means for refraining fromterrestrially reusing comprises means for refraining from terrestriallyreusing the at least one of the satellite radiotelephone frequenciesthat is used in the predetermined satellite cell in the satellitefootprint when the ancillary terrestrial component is located within thepredetermined satellite cell or within the spatial guardband.
 70. Anancillary terrestrial component according to claim 69 wherein thespatial guardband is sufficiently large to reduce interference betweenthe at least one of the satellite radiotelephone frequencies that isused in the predetermined satellite cell in the satellite footprint, andthe at least one of the satellite radiotelephone frequencies that isterrestrially reused outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 71. An ancillaryterrestrial component according to claim 69 wherein the spatialguardband is sufficiently large to prevent interference between the atleast one of the satellite radiotelephone frequencies that is used inthe predetermined satellite cell in the satellite footprint, and the atleast one of the satellite radiotelephone frequencies that isterrestrially reused outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 72. An ancillaryterrestrial component according to claim 69 wherein the means forterrestrially reusing comprises means for receiving the at least one ofthe satellite radiotelephone frequencies that is used in thepredetermined satellite cell in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband.
 73. An ancillary terrestrial component according to claim 69wherein the means for terrestrially reusing comprises means forreceiving the at least one of the satellite radiotelephone frequenciesthat is used in the predetermined satellite cell in the satellitefootprint and at least one other frequency that is used by thespace-based component in the satellite footprint, outside thepredetermined satellite cell and separated therefrom by the spatialguardband.
 74. An ancillary terrestrial component according to claim 69wherein the means for terrestrially reusing comprises means fortransmitting the at least one of the satellite radiotelephonefrequencies that is used in the predetermined satellite cell in thesatellite footprint, outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 75. An ancillaryterrestrial component according to claim 69 wherein the means forterrestrially reusing comprises means for transmitting the at least oneof the satellite radiotelephone frequencies that is used in thepredetermined satellite cell in the satellite footprint and at least oneother frequency that is used by the space-based component in thesatellite footprint, outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 76. An ancillaryterrestrial component according to claim 69 wherein the spatialguardband is about half a radius of a satellite cell in width.
 77. Anancillary terrestrial component according to claim 68 in combinationwith a plurality of radiotelephones that are configured to wirelesslycommunicate with the space-based component and/or the ancillaryterrestrial component.
 78. An ancillary terrestrial component accordingto claim 69 wherein the ancillary terrestrial component furthercomprises means for determining whether the ancillary terrestrialcomponent is located outside the predetermined satellite cell andseparated therefrom by the spatial guardband.
 79. An ancillaryterrestrial component according to claim 78 wherein the means fordetermining comprises means for receiving and/or processing of at leastone of the satellite radiotelephone frequencies of the satelliteradiotelephone frequency band.
 80. An ancillary terrestrial componentaccording to claim 78 wherein the satellite radiotelephone frequenciesinclude a plurality of Broadcast Control CHannel (BCCH) frequencies andwherein the means for determining comprises means for receiving and/orprocessing signal strength and/or content of at least one of the BCCHfrequencies.
 81. An ancillary terrestrial component according to claim78 further comprising means for transmitting results of the means fordetermining to at least a second ancillary terrestrial component.